1. Field of the Invention
The invention relates to a method and apparatus for receiving signals, in particular television (TV) signals, which are transmitted in accordance with different transmission standards. For example, in some European regions, TV transmissions of both the B/G-PAL type and of the D/K-PAL type may be received with a suitable multi-standard TV receiver.
2. Description of the Related Art
Multi-standard TV receivers suitable for reception of both B/G-PAL and D/K-PAL TV signals are known. Like other conventional TV receivers, these multi-standard receivers comprise a tuner, an intermediate-frequency (IF) filter circuit and a demodulator circuit. The tuner selects a desired TV signal and frequency-converts the desired TV signal to obtain a TV IF signal. The IF filter circuit passes the TV IF signal, which is provided by the tuner, to the demodulator circuit. In response to the filtered TV IF signal, the demodulator circuit provides a baseband video signal and a baseband audio signal. The demodulator circuit can operate in a B/G-mode and a D/K-mode for demodulating B/G-PAL TV signals and D/K-PAL TV signals, respectively.
Multi-standard TV receivers, like ordinary TV receivers, have to satisfy so-called EN55020 requirements in many European countries. One of the EN55020 requirements stipulates that no noticeable interference should occur in the baseband video signal, when an adjacent channel TV signal of a certain level is present. This is referred to as the interference immunity requirement.